In reply to Bob Cook's message of Thu, 15 May 2014 17:38:02 -0700: Hi, Nucleons are little magnets. Different orientations mean differing amounts of magnetic energy, hence different energy states for the nucleus as a whole. Obviously there is one combination of orientations which is less stressed than any of the others. This is the ground state. (Actually there may be several that are equally stable). Dave already answered the linear momentum question. As for the angular momentum of the gamma ray, that comes from spin flipping of a nucleon, e.g. from -1/2 to +1/2. When flipping the spin of any single nucleon would only result in a higher energy state of the nucleus rather than a lower one, while the nucleus is already in an excited state, then you have what is known as a meta-stable state. IOW the nucleus is essentially "stuck" in an energy rich state because it can't get the angular momentum needed for the gamma ray by flipping the spin of a single nucleon, (flipping the spin of multiple nucleons concurrently is far less likely, hence the "stuckedness". ;)
>Robin-- > >You stated: >>>Different combinations of spin states show up as excited >states of the nucleus. >Usually these relax to the ground state in short order with emission of a >gamma >ray.<<< > >How do spin states with no kinetic energy relax to a ground state with a >gamma ray emission with both angular momentum (spin) and kinetic energy >(linear momentum)? Where does the linear momentum come from? You raise >the question: When does linear momentum need to be conserved? Is it >conserved in nuclear transitions? > >Bob Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
